1. Field of the Invention
The present invention relates to a chair comprising a supporting structure having a seat and a backrest, in which the backrest comprises:
a deformable resting portion made of plastic material having a non-planar resting surface and provided with at least one weakened area that enables elastic deformation of the resting portion so that the resting portion assumes a configuration bent backwards under the action of a thrust applied backwards by the user;
two uprights formed integrally on the lateral sides of the resting portion; and
two side connection elements that connect the backrest to the supporting structure and are formed integrally at the bottom ends of the uprights.
2. Description of the Related Art
A chair of this type is known from the document No. EP-A-1557115, filed in the name of the present applicant. In the prior art chair, the backwards inclination of the backrest consists in part of an elastic deformation of the resting portion of the backrest and in part of a movement or a deformation of the connection elements that connect the backrest to the supporting structure. The resting portion and the side uprights of the backrest are made of a single injection-moulded plastic material. In the prior art chair, it is important to use for the production of the backrest a plastic material with good characteristics of rigidity in order to ensure the return of the backrest in the undeformed position when the thrust applied backwards by the user ceases. The plastic material used for the production of the backrest must moreover ensure that the backrest exerts a sufficient elastic thrust on the back of the user in the deformed position, given that the elastic reaction of the backrest has a marked impact from the standpoint of comfort.
To meet the aforesaid needs, the chair known from the document No. EP-A-1557115 must be made of a plastic material with high elastic properties, for example nylon.
To reduce the cost of production of the chair, it would be desirable to use a less costly plastic material, for example polypropylene. However, a less costly plastic material, such as for example polypropylene, would not present the elastic properties sufficient for guaranteeing proper operation of the backrest and the desired characteristics of comfort.
U.S. Pat. No. 6,669,301 discloses a chair comprising a seat and a backrest, both formed by a panel made of flexible plastic material, preferably polypropylene. The panel constituting the seat or the backrest is provided with a plurality of weakened areas constituted by through cuts. The panel comprises a continuous perimetral frame made of a second plastic material with a higher rigidity than that of the material constituting the panel. However, the continuous perimetral frame prevents the backrest from assuming a configuration bent backwards under the action of a thrust applied backwards by the user.
The purpose of the present invention is to provide a simple and inexpensive chair that will overcome the drawbacks of the prior art.